The present invention generally relates to aircraft antennas and more particularly to an antenna component that is a structural member of the aircraft.
Modern aircraft have a need to provide radio communication over a variety of frequency ranges and communication modes. For example, radio communication may be in the VHF band using amplitude modulation (AM) and/or frequency modulation (FM) or in the UHF band. In order to communicate effectively, the aircraft must include multiple antennas dispersed on the aircraft. Typically, the aircraft will include antennas mounted behind the radio transparent skin of the aircraft, and/or include exterior blade antennas mounted to the skin of the aircraft.
For effective communication, the antenna dimensions should be in the same order of magnitude as the wavelength of the signal being propagated. In this respect, the wavelength for operation in the VHF/AM and UHF band (i.e., 0.150 to 2.0 GHz) is approximately 0.1 to 2 meters. Accordingly, for effective communication within this range, the antenna must have a size correspondingly large. However, this is not practical because an antenna of this size would be aerodynamically inefficient. Therefore, small blade antennas electrically matched through impedance tuning networks are used. The blade antenna is a small fin protruding from the skin of the aircraft that is used as the radiating element.
Blade antennas are aerodynamically inefficient because they protrude from the skin of the aircraft. Typically, multiple blade antennas are used on the aircraft for the multiple communications band (i.e., UHF, VHF/FM, VHF/AM). The blade antenna exhibits poor performance characteristics at lower frequencies (i.e., 30-88 MHz). The blade antenna is constructed to withstand the forces subjected to the antenna, however the blade antenna is still susceptible to impact damage (i.e., break off). The blade antenna does not add any structural strength to the aircraft, and interferes with the aerodynamic efficiency of the aircraft.
In the prior art, antenna radiating elements have been embedded within the skin of the aircraft. Such radiating elements provide an antenna structure for the aircraft that is structurally integrated within the skin thereof. However, these prior art antenna structures are typically difficult to manufacture and install. Additionally, the prior art antenna structures do not exhibit ideal gain characteristics and fatigue life of these prior art antenna structures is significantly reduced due to the configuration of the antenna radiating element.
Specifically, the prior art antenna structures consisted of a spiral center fed radiating element embedded within the structure of the aircraft. The spiral center fed radiating element was difficult to install and did not exhibit desired gain and/or power characteristics. Furthermore, the antenna structure with the spiral center fed radiating element is not adaptable for existing aircraft. In this respect, the prior art antenna structure would need to be integrated into the original design of the aircraft.
The present invention addresses the above-mentioned deficiencies in prior aircraft antenna design by providing an antenna that is a structural member of the aircraft. In this respect, the aircraft antenna of the present invention is a structural member of the aircraft that can be adapted for multiple uses. The antenna structure of the present invention provides improved gain, higher power, improved fatigue life, and lower signature over the prior art spiral center fed antenna structure by using an end fed radiating element. Accordingly, the antenna structure of the present invention provides an improvement over the prior art inasmuch as the antenna exhibits desired operating characteristics.